The threads in alloy rings are more prone to stripping and alloys clamps that are over-tightened onto the rails milled into steel actions can also become a bit chewed up along the edges..

I prefer steel myself and prefer ring-mounts or one piece units if possible..

For a general purpose hunting rifle, I much prefer those with rails (or similar) milled into the action such as on Sako, Ruger or CZ's ect to negate the need for separate bases..To me, this is probably more important than if the ring-mounts are steel or alloy